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Plant growth-promoting bacteria (PGPB) afford plants several advantages (i.e., improvement of nutrient acquisition, growth, and development; induction of abiotic and biotic stress tolerance). Numerous PGPB strains have been isolated and studied over the years. However, only a few of them are available on the market, mainly due to the failed bacterial survival within the formulations and after application inside agroecosystems. PGPB strains with these challenging limitations can be used for the formulation of cell-free supernatants (CFSs), broth cultures processed through several mechanical and physical processes for cell removal. In the scientific literature there are diverse reviews and updates on PGPB in agriculture. However, no review deals with CFSs and the CFS metabolites obtainable by PGPB. The main objective of this review is to provide useful information for future research on CFSs as biostimulant and biocontrol agents in sustainable agriculture. Studies on CFS agricultural applications, both for biostimulant and biocontrol applications, have been reviewed, presenting limitations and advantages. Among the 109 articles selected and examined, the Bacillus genus seems to be the most promising due to the numerous articles that support its biostimulant and biocontrol potentialities. The present review underlines that research about this topic needs to be encouraged; evidence so far obtained has demonstrated that PGPB could be a valid source of secondary metabolites useful in sustainable agriculture.

Cultured meat production requires microcarriers, hydrogels, and scaffolds for 3D growth and support.Co-culturing techniques of probiotic bacteria and cell cultures are available.Probiotic bacteria efficiently produce antimicrobial substances, hydrogels, and fibril scaffolds.Probiotic bacteria can be genetically manipulated to grow only when it serves the cell culture.Probiotic bacteria can be genetically manipulated to serve as biosensors for lactate production and to remove lactate waste.Introducing probiotic bacteria into cultured meat can improve the design, function, and cost production and should be further explored. Cultivated meat is emerging to replace traditional livestock industries, which have ecological costs, including land and water overuse and considerable carbon emissions. During cultivated meat production, mammalian cells can increase their numbers dramatically through self-renewal/proliferation and transform into mature cells, such as muscle or fat cells, through maturation/differentiation. Here, we address opportunities for introducing probiotic bacteria into the cultivated meat industry, including using them to produce renewable antimicrobials and scaffolding materials. We also offer solutions to challenges, including the growth of bacteria and mammalian cells, the effect of probiotic bacteria on production costs, and the effect of bacteria and their products on texture and taste. Our summary provides a promising framework for applying microbial composites in the cultivated meat industry. Cultivated meat is emerging to replace traditional livestock industries, which have ecological costs, including land and water overuse and considerable carbon emissions. During cultivated meat production, mammalian cells can increase their numbers dramatically through self-renewal/proliferation and transform into mature cells, such as muscle or fat cells, through maturation/differentiation. Here, we address opportunities for introducing probiotic bacteria into the cultivated meat industry, including using them to produce renewable antimicrobials and scaffolding materials. We also offer solutions to challenges, including the growth of bacteria and mammalian cells, the effect of probiotic bacteria on production costs, and the effect of bacteria and their products on texture and taste. Our summary provides a promising framework for applying microbial composites in the cultivated meat industry.

Escherichia coli is primarily known as a commensal colonising the gastrointestinal tract of infants very early in life but some strains being responsible for diarrhoea, which can be especially severe in young children. Intestinal pathogenic E. coli include six pathotypes of diarrhoeagenic E. coli (DEC), namely the (i) enterotoxigenic E. coli, (ii) enteroaggregative E. coli, (iii) enteropathogenic E. coli, (iv) enterohemorragic E. coli, (v) enteroinvasive E. coli, and (vi) diffusely-adherent E. coli. Prior to human infection, DEC can be found in natural environments, animal reservoirs, food processing environments and contaminated food matrices. From an ecophysiological point of view, DEC thus deal with very different biotopes and biocoenoses all along the food chain. In this context, this review focuses on the wide range of surface molecular determinants acting as surface colonisation factors (SCFs) in DEC. In the first instance, SCFs can be broadly discriminated into (i) extracellular polysaccharides, (ii) extracellular DNA, and (iii) surface proteins. Surface proteins constitute the most diverse group of SCFs broadly discriminated into (i) monomeric SCFs, such as autotransporter (AT) adhesins, inverted ATs, heat-resistant agglutinins or some moonlighting proteins, (ii) oligomeric SCFs, namely the trimeric ATs, and (iii) supramolecular SCFs, including flagella and numerous pili, e.g. the injectisome, type 4 pili, curli chaperone-usher pili or conjugative pili. This review also details the gene regulatory network of these numerous SCFs at the various stages as it occurs from pre-transcriptional to post-translocational levels, which remains to be fully elucidated in many cases.

Municipal sewage sludge (MSS) is an inevitable byproduct of wastewater treatment, with increasing amounts year by year worldwide. The development of environmentally and economically acceptable methods for the sustainable management of MSS is a major environmental challenge. Nowadays, sludge management practices, besides the commonly used stabilization methods, focus attention on alternative sludge-disposal pathways, which encompass enhanced energy and valuable-resource recovery. This review presents the recent advances in the recovery of selected value-added products from sludge. Because of the high nitrogen and phosphorus concentrations, waste MSS can be a nutrient source (e.g., struvite). This paper discusses the conditions of and advances in the technology of struvite recovery. As in the extracellular polymeric substances (EPSs) of biological sludge, alginate-like exopolymers (ALEs) are present in MSS systems that treat municipal wastewater. The yields, dynamics in content, and characterization of ALEs and their possible applications were analyzed. MSS is an important source of humic substances. Their occurrence, characterization, and yields in various types of MSS (e.g., untreated, composted, and digested sludge) and main methods of application are presented. The important aspects and trends of MSS pyrolysis, including the thermochemical conversion to biochar, are discussed in this review. The characterization of biochar derived from MSS and the assessment of the environmental risks are also covered. This paper explores the potential use of biochar derived from MSS in various applications, including soil amendment, carbon sequestration, and environmental remediation.

Microbial exopolymers [extracellular polymeric substances (EPS)] produced from waste(water) are emerging nature-based, biodegradable, nontoxic alternatives to synthetic flocculants.High carbon recovery into biopolymers can be achieved through overproduction of EPS from nitrogen-limited waste(water) at limited specific mineralization rates (20–40% COD) from pure glycerol and industrial wastewater.Production of EPS with net anionic charge and high molecular weight was achieved using actual industrial waste(water) with recovery efficiencies comparable to those obtained with pure cultures and/or synthetic wastewater.High flocculation potential comparable to anionic polyacrylamide (aPAM) was obtained when using either untreated EPS-rich mixed liquor or extracted EPS therefrom on dual-clay dispersions, with EPS flocculation behavior closely connected to molecular weight.Differences in viscosity of the mixed liquor had a direct influence in oxygen mass transfer resulting in lower or similar aeration demand to pure-culture production of exopolymers (e.g., xanthan gum). Flocculants are widely used for solid–liquid separation despite environmental risks such as microplastics accumulation or release of toxic compounds. Microbially-secreted biopolymers are potential biodegradable, nontoxic alternatives. We demonstrate the feasibility of overproducing microbial exopolymers [extracellular polymeric substances (EPS)] from glycerol- and carbohydrate-rich industrial waste(water) in open-culture bioreactors. Two semi-pilot scale airlift bioreactors were operated with (airlift-MBR) and without membrane (airlift) to treat pure glycerol, biodiesel wastewater, and potato starch hydrolysate. Efficiency of EPS production with respect to supplied chemical oxygen demand reached values of 42% from pure glycerol, 30% from biodiesel wastewater, and 22% from potato starch hydrolysate. The airlift bioreactor showed stable continuous operation compared to airlift-MBR which was affected by membrane fouling. The produced EPS had net anionic charge and high molecular weight between 1 and 2.5 MDa. Both untreated EPS-rich mixed liquor produced in the bioreactors and extracted EPS therefrom showed promising flocculation potential comparable to anionic polyacrylamide. [Display omitted] Microbially-secreted biopolymers produced from second-generation biomass sources are potential alternatives to fossil-based flocculants, with the inherent advantages of being biobased, biodegradable, and nontoxic polymers. The dedicated production of microbial exopolymers (EPS) in open-culture bioreactors to obtain anionic natural flocculants from waste(water) is currently validated in laboratory and semi-pilot systems [technology readiness level (TRL), 4–5]. Sustained EPS overproduction with reliable flocculation activity has been successfully obtained over long-term operation of continuous bioreactors from synthetic and industrial wastewater. This adds to the range of bioproducts attainable through open-culture biotechnology, next to methane, short- and medium-chain carboxylates, and polyhydroxyalkanoates (PHA), among others. To realize this vision, future research should: (i) demonstrate flocculant EPS effectiveness on real wastewater, (ii) optimize flocculation by elucidating mechanisms and kinetics, and (iii) broaden the range of feedstocks suitable for EPS overproduction. The design of advanced processes for microbial flocculants production will benefit from further characterization of the metabolic conversions and non-Newtonian fluids prevailing within EPS-overproducing bioreactors as well as a deep understanding of structural and physicochemical properties of native and processed exopolymers. Technological developments needed for full-scale implementation include engineering EPS flocculation capacity and versatility to target diverse industrial applications; cost-effective production comparable with synthetic flocculants; and pilot-scale demonstrations of microbial flocculants both production and application under relevant industrial conditions to achieve TRL 6–7. Other aspects to be achieved are the end-of-waste status of waste-derived biopolymers and the creation of regulatory drivers promoting the transition away from low-priced synthetic polymers to favor the adoption of nontoxic, risk-free biobased flocculants. Key research areas are (i) understanding the bioenergetics of open-culture EPS overproduction and their effects on EPS characteristics, (ii) understanding the relation between EPS characteristics and underlying interactions with colloidal particles to optimize flocculation, and (iii) designing processes that ensure competitive flocculant EPS production. There is an increasing need for finding cost-effective alternatives to synthetic polymers. We demonstrate sustained production of microbial exopolymers from wastewater, with flocculating properties comparable to commercial polyacrylamide. This technology enables upcycling of residual feedstocks to increase circularity in water treatment and avoid chemicals with negative health and environmental impacts.

Background is provided on biofilms, including their formation, tolerance mechanisms, structure, and morphology within the context of chronic wounds. The features of biofilms in chronic wounds are discussed in detail, as is the impact of biofilm on wound chronicity. Difficulties associated with the use of standard susceptibility tests (minimum inhibitory concentrations or MICs) to determine appropriate treatment regimens for, or develop new treatments for use in, chronic wounds are discussed, with alternate test methods specific to biofilms being recommended. Animal models appropriate for evaluating biofilm treatments are also described. Current and potential future therapies for treatment of biofilm-containing chronic wounds, including probiotic therapy, virulence attenuation, biofilm phenotype expression attenuation, immune response suppression, and aggressive debridement combined with antimicrobial dressings, are described.

Biofilms represent the main mode of existence of bacteria and play very significant roles in many industrial, medical and agricultural fields. Analysis of biofilms is a challenging task owing to their sophisticated composition, heterogeneity and variability. In this study, biofilms formed by the rhizobacterium Azospirillum baldaniorum (strain Sp245), isolated biofilm matrix and its macrocomponents have for the first time been studied in detail, using Fourier transform infrared (FTIR) spectroscopy, with a special emphasis on the methodology. The accompanying novel data of comparative chemical analyses of the biofilm matrix, its fractions and lipopolysaccharide isolated from the outer membrane of the cells of this strain, as well as their electrophoretic analyses (SDS-PAGE) have been found to be in good agreement with the FTIR spectroscopic results.

During screening for novel emulsifiers and surfactants, a marine gammaproteobacterium, Halomonas sp. MCTG39a, was isolated and selected for its production of an extracellular emulsifying agent, P39a. This polymer was produced by the new isolate during growth in a modified Zobell’s 2216 medium amended with 1% glucose, and was extractable by cold ethanol precipitation. Chemical, chromatographic and nuclear magnetic resonance spectroscopic analysis confirmed P39a to be a high-molecular-weight (~ 261,000 g/mol) glycoprotein composed of carbohydrate (17.2%) and protein (36.4%). The polymer exhibited high emulsifying activities against a range of oil substrates that included straight-chain aliphatics, mono- and alkyl- aromatics and cycloparaffins. In general, higher emulsification values were measured under low (0.1 M PBS) compared to high (synthetic seawater) ionic strength conditions, indicating that low ionic strength is more favourable for emulsification by the P39a polymer. However, as observed with other bacterial emulsifying agents, the polymer emulsified some aromatic hydrocarbon species, as well as refined and crude oils, more effectively under high ionic strength conditions, which we posit could be due to steric adsorption to these substrates as may be conferred by the protein fraction of the polymer. Furthermore, the polymer effected a positive influence on the degradation of phenanthrene by other marine bacteria, such as the specialist PAH-degrader Polycyclovorans algicola. Collectively, based on the ability of this Halomonas high-molecular-weight glycoprotein to emulsify a range of pure hydrocarbon species, as well as refined and crude oils, it shows promise for the bioremediation of contaminated sites.

The value of distinguishing native from nonnative invasive species has recently been questioned. However, this dichotomy is important for understanding whether a species’ successful dominance is caused by introductions, changing environmental conditions that facilitate an existing population, or both processes. We highlight the importance of knowing the origin of hard-to-detect invasive microorganisms for scientific research, management, and policy using a case study of recent algal blooms of the stalk-producing diatom Didymosphenia geminata. Nuisance blooms have been reported in rivers worldwide and have been hastily attributed to introductions. However, evidence indicates that blooms are probably not caused by introductions but, rather, by environmental conditions that promote excessive stalk production by this historically rare species. Effective responses to invasive microorganisms depend on knowing whether their proliferation is caused by being nonnative or is the result of changing environmental conditions that promote invasive characteristics of native species.

The EPS-producing Pseudoalteromonas sp. MER144 was selected among 606 isolates from Antarctic seawater due to its evident slimy appearance on agar plates. The production of EPSs was enhanced by a step-by-step approach varying the carbon source, substrate and NaCl concentrations, temperature, and pH. Optimal conditions for the EPS production resulted at temperature of 4 °C and pH 7, with addition of 2% sucrose ( w / v ) and 3% NaCl ( w / v ). EPSs produced under optimal conditions were chemically characterized, resulting in a moderate carbohydrate content (35%), uronic acids (14%), and proteins (12%). Monosaccharide composition was estimated to be Glu:Man:GluN:Ara:GluA:GalA:Gal (1:0.36:0.26:0.06:0.06:0.05:0.03), while the estimated molecular weight was about 250 kDa. The addition of sucrose in the culture medium, by stimulating the EPS production, allowed MER144 to tolerate higher concentrations of mercury and cadmium. This finding was probably dependent on the presence of uronic acids and sulfate groups, which can bind cations, in the extracted EPSs. Monitoring EPS production under optimal conditions at different concentrations of mercury and cadmium revealed that EPS amounts increased at increasing heavy metal concentrations, indicating an adaptation to the stress conditions tested.